<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>左不动，右随意</title>
    <!-- 重点左边width: 250px;  右边： margin-left: 250px; -->
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .lstop {
           height: 700px;
           background-color: rgb(186, 143, 150);
        }
        .lstop .lstop_left {
            float: left;
            width: 250px;
            height: 100%;
            background-color: rgb(180, 147, 197);
        }
        .lstop .lstop_right {
            height: 100%;
            margin-left: 250px;
            background-color: rgb(71, 71, 184);
        }
    </style>
</head>
<body>
    <div class="lstop">
        <div class="lstop_left"></div>
        <div class="lstop_right"></div>
    </div>
</body>
</html>